(Not Applicable)
1. Field of the Invention
The present invention relates to a reusable mat system for the construction of load bearing surfaces, such as temporary roadways and equipment support surfaces, over unstable or unsubstantial terrain. More particularly, the present invention relates to a reusable system of durable, interlocking individual mats which can be quickly and easily installed in a single application to construct temporary roadways and equipment support surfaces, and which can thereafter be easily removed and stored until needed again. More particularly still, the present invention relates to a reusable mat system comprising generally identical mats constructed of thermoplastic resins or other moldable materials, which interlock on all sides to form stable and continuous load bearing surfaces, and which exhibit favorable traction characteristics.
2. Description of the Related Art
When performing operations with heavy equipment in a remote location, it is often necessary to provide a firm, stable and continuous surface to support such heavy equipment. For example, when drilling a well in a remote location, it is often necessary to provide work surfaces used during the drilling process. It is also advantageous to provide one or more roadways to permit ingress to and egress from said remote location. Such a surface must provide sufficient support for the equipment and personnel involved in the work process, and must be able to withstand severe weather. Further, such a support surface must be capable of being quickly and easily installed, and thereafter being easily removed and reused at other locations.
Wooden boards or planks have historically been used to construct temporary roadways and equipment support surfaces in remote or undeveloped areas where the terrain lacks sufficient integrity to adequately support trucks and other heavy equipment. Such boards were generally placed end to end, or side by side, to form a continuous load supporting surface. While individual wooden boards or planks have been used to construct support surfaces for some time, this method of building roadways and other load bearing surfaces suffers from some very significant disadvantages.
Because such a large number of individual wooden boards are generally required to construct a typical roadway or equipment support surface, the use of wooden boards can be very labor intensive, since each board must first be individually positioned, and thereafter nailed or otherwise secured in place. Removal of said individual boards can also be a very time consuming and labor intensive process, since each board must be separated or pulled apart prior to being removed from the location. Each individual board must also be loaded onto a truck or other means of transportation prior to being removed from the particular location or work site.
In order to overcome the aforementioned shortcomings associated with the use of individual boards, a variety of mat systems have been developed for the construction of temporary roadways and support surfaces. These mat systems typically utilize prefabricated, multi-layered wooden mats which can be installed in a variety of configurations to create roadways or other support surfaces. These mats, which are constructed of a number of individual boards or planks affixed together in a variety of configurations, generally interconnect or inter mesh with one another to form a continuous, or nearly continuous, support surface.
While such conventional mat systems may represent an improvement over the use of individual boards for the construction of roadways and other equipment support surfaces, the aforementioned conventional mat systems suffer from a number of serious shortcomings. Although such conventional mats may reduce labor requirements compared to individual wooden boards, significant amounts of time, effort and manpower are still required to install said mats at a remote location since most, if not all, of said conventional mat systems require the use of multiple layers. In other words, an initial layer must first be installed, then at least one additional layer of mats must be installed over said first layer. This multiple layer requirement leads to significant redundancy of effort in connection with both the installation and removal of said mats.
Additionally, the design of conventional mat systems can lead to degradation of the ground underlying said mats, as well as the structural integrity of the mats themselves. Because the individual mats of conventional mat systems are generally constructed of various configurations of wooden boards or planks, conventional mats contain gaps or seams between said boards and/or planks. As rain falls on said mats, the rain water passes through the seams of said mats and mixes with the underlying soil to make mud. Trucks and other heavy equipment passing over the mats place a downward load on said mats, which in turn causes mud to be pumped up through the numerous gaps or seams of the mats. This pumping action creates voids beneath the mats which, over time, can lead to severe deformities in the roadway surface. Because the mats bridge over these underlying voids, the mats thereafter have a tendency to break or splinter when subjected to loading from above, especially after such wooden mats dry out.
Conventional wooden mats also suffer from significant rotting problems, since the mats can become inundated with rain water and various other contaminants from above, as well as mud from below. This mixture of water, mud and other contaminants will often invade into the seams or gaps between the boards of said mats, causing the wooden mats to rot from within. As a result, just as with individual boards, conventional mats must be frequently repaired and, in some cases, entirely replaced. Although conventional mat systems are designed to be reusable, the mats are still subject to significant repair and replacement expense. The design of these conventional mats can also lead to significant environmental problems, because mud and other contaminants can saturate the mats and collect within the numerous seams or gaps of said mats.
Yet another shortcoming with existing mat systems is the failure of individual mats to lock or interconnect with one another on all sides. Because the intended use of the mats dictates that the roadway or support surface will be subjected to loading from heavy equipment, often in different lateral directions, it is advantageous for individual mats to interconnect on all sides. This will prevent the individual mats from separating or xe2x80x9cwalking apartxe2x80x9d from one another, and will promote a continuous and uniform work surface.
Mat systems have been known in the art for some time. U.S. Pat. No. 2,819,026 to Leyendecker, describes a mat system wherein individual mats interconnect on two sides, and which further requires the use of a strap means for retaining said mats in a desired position.
U.S. Pat. No. 4,462,712 to Penland describes a mat system comprised of individual mats which contain interlocking fingers and recesses, but which interlock on only two sides. Similarly, U.S. Pat. No. 5,087,149 to Waller and U.S. Pat. No. 4,600,336 to Waller also disclose mat systems employing individual mats with alternating offset extensions and recesses along the edges of said individual mats. However, said patents describe offset extensions comprised of individual planks which are subject to warpage, cracking or splintering when exposed to environmental elements, as well as loading from trucks or other heavy equipment using the work surface. Moreover, unlike the present invention, these offset extensions often need to be nailed in place to be secured within the recess of an adjacent mat. The referenced patents to Waller also describe the additional step of securing a plank or board between the individual mats, which significantly increases labor requirements associated with these mat systems.
U.S. Pat. No. 5,273,373 to Pouyer; U.S. Pat. No. 5,316,408 to Stanley, et al.; U.S. Pat. No. 4,875,800 to Hicks and U.S. Pat. No. 4,973,193 to Watson et al. all describe mat systems which are installed in multiple layers or stages. This factor makes the installation process significantly more complicated than that of the present invention, and greatly increases labor costs associated with said installation.
U.S. Pat. No. 4,629,358 to Springston discloses a mat system for the construction and repair of airfield surfaces. The individual mats described in the ""358 patent are fiberglassxe2x80x94reinforced plastic composite mats which include hollow inorganic silica spheres for weight reduction purposes. Although the mats disclosed in the ""358 patent exhibit a generally similar outer configuration to the mats of the present invention, the mats described in the ""358 patent do not contain integral internal cellular structure. Moreover, the airfield mats of the ""358 patent, unlike the preferred embodiment of the mats of the present invention, are not constructed of two mirror-image panels or half-mats which are joined together to form a complete single mat.
U.S. Pat. No. 5,653,551 to Seaux also describes a mat system for the construction of roadways and equipment support surfaces comprised of individual mats containing internal cellular structure. However, the mats disclosed in the ""551 patent do not include traction promoting elements in the form of raised strips extending outward from the planar surfaces of the individual mats. More significantly, the ""551 patent does not disclose the placement of such raised strips proximate to, and in general alignment with, the internal cell forming walls of the individual mats. In addition, the mats disclosed in the ""551 patent contain offset peripheral edges, but lack means for mechanically affixing said mats to adjacent mats.
U.S. Pat. No. 5,888,612 to Needham, et al, discloses load bearing structures which can be molded from thermoplastic resin, and which have internal cellular structure. However, the individual mats described in the ""612 patent have a dramatically different outer configuration than the mats of the present invention. Further, the mats described in the ""612 patent also lack traction promoting elements on the outer planar surfaces of said mats, as well as means for mechanically joining said mats to other adjoining mats.
The prior art in general, and the aforementioned patents in particular, fail to disclose a mat system having the advantages of the invention disclosed herein.
The mat system of the present invention is a durable, reusable mat system which can be utilized to construct roadways and other support surfaces. Moreover, the mat system of the present invention can be horizontally expanded in all lateral and longitudinal directions to provide the desired coverage by the roadway or other support surface being constructed. Due to the generally uniform outward configuration of the individual mats of the present invention, a roadway and/or other support surface can be installed in a single layer by simple placement of the individual mats. Additionally, this generally uniform outward configuration allows for great flexibility in the installation process. These qualities greatly reduce the time, expense and labor requirements associated with installing and removing the disclosed invention.
The mat system of the present invention further comprises individual mats which are impermeable, so that fluids cannot seep through said mats. For this reason, the pumping effect observed with other conventional mats is effectively eliminated, and deterioration of the underlying terrain is thereby greatly reduced. The individual mats of the mat system of the present invention are also lighter than mats of most conventional mat systems, which allows for more efficient and economical transportation of said mats to and from installation locations.
Because the mats of the present invention possess substantially continuous outer surfaces, there are no gaps or channels in which mud and other contaminants can accumulate. Further, the mats of the present invention can be easily washed to remove any mud or other contaminants which may adhere to the outer surfaces of said mats. These qualities prevent the spread of contaminants from one installation location to another.
The dimensions of the individual mats of the present invention can be varied to fit particular uses and/or applications. In the preferred embodiment, the lateral dimensions of the individual mats of the present invention are approximately eight (8) feet wide by fourteen (14) feet long. Again, it must be stressed that these dimensions are not a limitation; the dimensions of the individual mats of the present invention can be changed as necessary to fit a particular application. As such, although it is generally beneficial for all individual mats of the mat system of the present invention to be roughly the same size as one another, it may be desirable to have a number of mats of different dimensions to customize the shape of a work surface or permit placement of mats where space may be limited.
Traction promoting elements are provided on the planar surfaces of the individual mats of the present invention. Said traction promoting elements are utilized to improve frictional characteristics of said mats, thereby improving traction for vehicles and other equipment traveling across roadways and other support surfaces constructed from the mat system of the present invention. Ideally, said traction promoting elements are raised members extending outward from the planar surfaces of the individual mats of the invention described herein. A large number of said raised members are beneficially positioned proximate to, and in general alignment with, the cell walls defining the internal cellular structure of said individual mats. In the preferred embodiment, wherein the cellular structure of the individual mats is in the shape of a plurality of hexagonal honeycombs, said traction promoting elements are corresponding in the form of raised strips extending outward from the planar surfaces of the individual mats of the present invention, and defining a plurality of generally star-like patterns on said planar surfaces.
When significant weight is placed on the individual mats of the present invention, such as when said mats are subjected to downward loading from trucks or other heavy equipment, said raised traction promoting elements are likewise subjected to heavy loading. Because said traction promoting elements represent substantially less surface area than the planar surfaces of said individual mats, such loading will tend to be focused or concentrated on said traction promoting elements. When such raised members are positioned proximate to, and in alignment with, the internal cell forming walls of the individual mats, said cell forming walls provide direct support for loading. However, when a large number of such raised members are not positioned in such a manner, the relatively thin outer skin defining the roughly planar surfaces of the mats can become easily deformed by such direct loading.
In addition to said traction promoting raised elements, the preferred embodiment of the mats of the present invention also include traction promoting anti-skid planar surfaces. Such anti-skid surfaces can be affixed to the mats or molded into said mats by overmolding a thin layer of traction promoting material on the work surface of said mats. In the preferred embodiment, said mats are molded primarily of thermoplastic resin. During the molding process, a relatively thin surface layer of low density material is overmolded across the bulk thermoplastic resin. Although any number of materials can be contemplated for this purposes, low density polyethylene (xe2x80x9cLDPExe2x80x9d) or very low density polyethylene (xe2x80x9cVLDPExe2x80x9d) can be used for this purpose in the preferred embodiment. Said low density material exhibits a greater coefficient of friction than the bulk resin used to mold the mats, which in turn promotes the anti-skid quality of said surface layer. Further, to the extent that said mats are molded out of thermoplastic resin, any number of additives can be included within the mats to meet or otherwise improve desired characteristics. For example, in the preferred embodiment, it may be beneficial to include one or more additives to control the static electricity characteristics of the mats.
In the preferred embodiment of the present invention, the individual mats are constructed of two mirror-image half-pieces which are joined together to form a complete single mat. Said half-pieces are comprised of at least one area of reduced material consisting of a planar skin having cell forming walls which extend outward in roughly perpendicular fashion from said planar skin and which define open faced cellular structure. Each of said half-pieces also have two adjacent edge areas without exposed cellular structure that exhibit characteristics similar to solid structure; that is, said adjacent edges have roughly continuous outer surfaces on all sides. In order to form a single mat, two mirror-image half-pieces are affixed together, such that the areas of said half-pieces which exhibit open-faced cellular structure are aligned with, and directly adjacent to, one another.
The half-pieces of the present invention can be affixed together by a variety of means. For example, said half-pieces can be welded or glued together to form a complete mat. Such welding can be performed across the opposing surfaces of the half-pieces, or along the peripheral seam between said half-pieces. Additionally, mechanical fasteners such as screws and nuts, or rivets, can be used to join said half-pieces to one another. Furthermore, various combinations of such joining methods can be employed to affix said half-pieces to one another. In the preferred embodiment, a combination of mechanical fasteners and peripheral welding is used to affix said mirror-image half-pieces to one another to form a single, complete mat.
Additionally, it is desirable to utilize a plurality of rigid inserts between the mirror-image half-pieces of the present invention. Such inserts are beneficially shaped to fit within corresponding opposing cells of two half-pieces which are joined together to form a complete mat. In the preferred embodiment, such inserts are generally hexagonal in shape to correspond to the hexagonal shaped open-faced cells of the half-pieces of the present invention.
When the mats of the present invention are used to construct a roadway or support surface, particularly in a remote location, it is not uncommon for said mats to be exposed to large temperature changes. Often, one planar surface of a mat will be exposed to direct sunlight, while the opposite planar surface will be face down and therefore obscured from such sunlight. As a result, although two half-pieces are permanently affixed to form a single complete mat, a temperature differential can nonetheless exist between such half-pieces. This temperature variance can result in a differential in shrinkage rates between said half-pieces which can, in turn, generate forces which cause said half-pieces to curl and/or pull apart from one another. Rigid inserts placed within opposing cells of two half-pieces will help to offset such forces. Such rigid inserts help keep the half-pieces aligned with one another, and help resist differential shrinkage. Further, such rigid inserts also can improve overall stiffness characteristics of said mats. In applications where greater stiffness is required, a greater number of rigid inserts can be used.
As trucks or other vehicles travel across roadways or other support surfaces constructed from the mat system disclosed herein, mats of conventional mat systems can have a tendency to pull or xe2x80x9cwalk apartxe2x80x9d from one another. It is possible for such a roadway or other surface constructed of the mat system of the present invention to remain roughly intact and useable without means of linking said mats together. However, in the preferred embodiment, the peripheral edges of said mats contain receptacles for receiving fastening devices. Such fastening devices act to mechanically affix the mats together, and thereby prevent said mats from pulling away from one another after being installed at a remote location. Any number of different configurations of receptacles and/or fasteners can be utilized. However, in the preferred embodiment, said receptacles are spaced in a consistent manner. Along the long edge of each mat, said receptacles are spaced in a group of three near the center of said mat, while an additional receptacle is positioned near each end of said long edge. Two receptacles are also located along the short edge of each mat. Additionally, a receptacle is positioned near the corners of the mat between said long and short sides.
It is therefore an object of the present invention to provide a durable, reusable mat system which can be utilized to construct roadways or other support surfaces.
It is a further object of the present invention to provide a mat system wherein horizontal expansion of the desired roadway and/or equipment support surface is accommodated in all longitudinal and lateral directions.
It is a further object of the present invention to provide a mat system wherein the individual mats of said system are restrained from horizontal movement by frictional contact with the underlying terrain, and mechanical contact with adjoining mats.
It is a further object of the present invention to provide a mat system comprising a plurality of wholly interchangeable individual mats which can be installed in a single layer by simple relative placement.
Other and additional objects of the invention are apparent throughout the details of construction and operation as more fully described herein and illustrated in the accompanying drawings.